The present invention relates generally to monitoring systems for machinery. More particularly, the invention relates to a monitoring system that is readily integrated into a standard industrial control architecture.
Industrial controllers are special purpose computers that are used for the control of industrial processes or manufacturing equipment. Under the direction of a stored program, the industrial controller examines a series of inputs representing the state of the controlled process and changes outputs effecting the control of the process. The inputs and outputs may be binary, for example, on or off, or alternately, analog inputs and outputs taking on a continuous range of values. The inputs are typically from sensors including limit switches and the like, and the outputs may be provided to actuators, motors, and the like.
Normally, the components of an industrial process are spatially distributed about the factory or manufacturing facility. The industrial controller may communicate with these components via one or more remote I/O modules connected to the industrial controller through a specially designed control network such as ControlNet, DeviceNet or Ethernet/IP whose specifications are published and whose protocols are used broadly by a number of manufacturers and suppliers. These communication networks are characterized by being highly reliable and delivering data with a minimal and well-characterized delay as required for real-time control and may be implimented on dedicated network media, backplanes of devices, and/or wirelessly.
The machines of an industrial process may be monitored with monitoring equipment to assess the health of the machinery on a real-time basis and to predict and possibly avoid expensive failure. Such monitoring systems typically use high data-rate sensors, such as accelerometers and the like that may be, for example, attached to a bearing or journal to provide vibration data that may reflect impending equipment failure.
These sensors normally are wired to a signal processing engine that continually measures the signal and processes out key information from it. These signal processing engines are often linked to common computers, usually by standard Ethernet interfaces, that execute specialized software that can further process the data and provide a report to a user. Depending on the sophistication of the software system, the report will either provide the data necessary for an expert to evaluate the machines health, and/or it will, after applying a set of rules, provide its own evaluation of the machines condition. Vibration data, for example, may be analyzed for specific frequency components which might indicate wear of bearings used in high-speed machines or shaft misalignment. These computer systems and, more specifically, the sophisticated software required can be very expensive and requires a continuing investment in time-consuming operation by experts. Further, such systems are not typically real time systems. Most require data be uploaded from the protection monitors are defined schedules and the data or reports evaluated by experts sometime later. Few systems are integrated with operations such that data is evaluated and meaningful results immediately provided to the machine's operators immediately when changes are detected.
The problems associated with installing a monitoring system have been significantly reduced by the development of a set of “modular” signal processing engines, (also called monitoring modules) described in U.S. Pat. Nos. 6,662,118; 6,768,949; and 6,912,484, all incorporated by reference, that connect directly to the networks normally used in industrial control systems. Such connection allows monitoring to use the same communications infrastructure already present in many industrial control environments and further allows data to be communicated directly with a programmable logic controller, so that corrective action may be automatically initiated.
Each signal processing engine provides interface circuitry for the control network and for the type of sensors used in protection or monitoring applications, for example, accelerometers and high-speed displacement transducers. Importantly, the signal processing engines provide for pre-processing of the sensor data, for example, performing Fourier transform of accelerometer data and analyzing the spectrum against pre-defined bandwidths and amplitude or power thresholds. In this way, the high data-rate vibration data, for example, need not be communicated directly over the control network but rather only low data-rate “dynamic condition data” need be communicated. For example, vibration data is not transmitted but only dynamic condition data indicating that a particular frequency threshold has been exceeded. This prevents degradation of the control network's function of providing real-time control.
To provide flexibility, the signal processing engines normally have alterable configuration data, for example, defining particular frequency limits or bands describing the pre-processing to be performed by the signal processing engines.
While such signal processing engines are a considerable advance in simplifying and integrating machine monitoring into an industrial control system, they still require considerable expertise for configuring the signal processing engines and programming the industrial controller to interpret the operating assessments, particularly for installations where multiple signal processing engines are required. For example, some forms of failure detection may require monitoring of axial and radial acceleration at different points in the operation of the machine in different frequency bands depending on the particular control task being executed at that time. Determining the necessary modules and sensors and how they should be integrated together may still be challenging.